Human immunodeficiency virus type 1 (HIV-1)-seronegative injection drug users at risk for HIV exposure have antibodies to HLA class I antigens and T cells specific for HIV envelope

The question of whether persistently seronegative persons at high risk for human immunodeficiency virus type 1 (HIV-1) infection exhibit HIV-1-specific T cell responses and antibodies to HIV-1 envelope epitopes shared with selected HLAs was assessed, These antibodies are not detectable by conventional serologic methods, Envelope-specific helper T (Env-Th) cell responses and antibodies specific for the HIV/HLA epitopes were studied in 21 HIV-1-negative injection drug users (IDUs), HIV/HLA antibodies were detected in 7 (33.3%) of 21 IDUs and 4 (4.3%) of 94 low-risk controls, Env-Th cell responses were detected in 16 (76.2%) of 21 IDUs and in 2 (3.1%) of 65 low-risk controls, All HIV/HLA antibody-positive IDUs also had Env-Th cell responses, These findings confirm the presence of HIV-1-specific immunity in conventionally seronegative individuals, Further characterization of these responses could provide the basis for new preventive strategies.